<!DOCTYPE html>
<html>
<head>
	<title></title>
	<style type="text/css">
	*{margin:0;padding:0;}
	ul{
		list-style: none;
		border:10px solid #ccc;
		/*overflow: hidden;*/
	}
	ul:after{
		content: '';
		display: block;
		clear: both;
	}
	ul li{
		float:left;
		width: 100px;
		height: 100px;
		background: red;
	}
	/*div{
		clear: both;
	}*/
	</style>
</head>
<body>

<ul>
	<li>1</li>
	<li>2</li>
	<li>3</li>
	<!-- <div></div> -->
</ul>

</body>
</html>